Frame understructures used in environments subject to great physical stress are well-known in the art. For example, one type frame understructure is used in the vertical tail section of military aircraft such as, for example, the F-16 fighter jet manufactured by Lockheed. The vertical tail structure typically consists of numerically controlled (NC) machined C-channel spars and ribs mechanically fastened together. The outboard panel of the aileron is a bonded assembly, typically comprising graphite/epoxy skins bonded to aluminum honeycombed core and mechanically fastened to the NC machined aluminum periphery structure. While this bonded assembly is considered to be one of the lightest possible structure configurations, there are substantial manufacturing risks associated with bonding dissimilar metals and materials as well as the normal risks associated with the bonding assembly.
Milling a frame from a single block of metal is also well-known in the art. Unfortunately, these previously designed or manufactured substantially integrated understructures required additional supports afterward or lacked strong rigidity necessary for high stress environments. Further, these prior solutions suffered from the drawbacks of having high waste byproducts as well as long lead times for manufacture and development and high expense relative to previously available frame structures.
Accordingly, there is a need for an improved method of manufacturing highly integrated understructures that overcome the prior problems of undue waste, high lead time, and great expense in design preparation and manufacture.